The primary automatic transmission to work with a torque converter (in place of a fluid coupling) was the Buick Dynaflow, which was released to the 1948 design yr. In regular driving, the Dynaflow utilized only the prime gear, relying on the torque multiplication of the torque convertor at lower speeds. https://gearbox-auto19527.answerblogs.com/34362924/gearbox-auto-for-dummies